The computer or communication control rooms is generally provided with a standby battery set ready to be put into service on an emergency basis at such time when the outage of electric power or failure of a rectifier takes place. The standby battery set is kept ready to be put into service at any moment by being connected with the floating charge of the rectifier. The standby battery set is , in fact, a part of the power system for providing the computer or communication equipment with an uninterrupted supply of direct current. However, the battery set will not be ready for service until such time when the initial charge, the discharge test, and the recharge of the battery set are completed.
The standby battery set of the power system is vulnerable to failure due to such factors as the fall-off of the activated (effective) material, the hardening of the negative or positive plate, etc. In view of these factors, the battery capacity is gradually deteriorated, whereas the internal resistance of the battery is progressively increased. Even if the battery set contains only one or two bad batteries, the overall function of the battery set can be adversely affected in view of the fact that the battery set is made up of a plurality of batteries which are connected in series, and that the inadequate residual capacity and the excessive internal resistance of the bad batteries can bring about a reverse charge at such time when the discharge of the battery takes place. It is therefore readily apparent that the residual capacity and other characteristics of the battery set must be monitored from time to time so as to ensure that the operation of the computer or communication system is not paralyzed in the event of a power outage.
The conventional method for testing the residual capacity of a battery set involves the separation of the battery set from the computer or communication system before the battery set is connected with a dummy load, such as a resistance, for doing a discharge test. The current and the time of the discharge test are dependent on the ampere-hour capacity of the battery. Generally speaking, the discharge test lasts eight or ten hours. Take a battery (3200AH) as an example. The discharge test of the battery lasts eight hours, whereas the current is 400 A. For the capacity test of each battery set, it is necessary to do the discharge for several hours and the recharge for more than 10 hours, so as to evaluate the capacity of the battery set. In addition, the test must be manned such that the voltage, the specific gravity of the electrolyte, the temperature of each battery of the battery set must be recorded. Such work assignments are time-consuming and costly. Take a local area communication system as an example, the standby battery set consists of at least 24 batteries. It is indeed too expensive to check the residual capacity and other characteristics of each of the 24 batteries.
With a view to overcoming the deficiencies of the conventional test method described above, this inventor of the present invention discloses in the U.S. Pat. No. 5,387,871 an advanced method for testing the characteristics of a battery set. The method makes use of a multiple loop voltage tester via which the data of the voltage and the current of each battery of the battery set are recorded in a computer during the charging-discharging period of the test. Upon completion of the charging-discharging test, the internal resistances of each battery during the charging period and the discharging period are computed by the computer on the basis of the terminal voltage of each battery. The internal resistance characteristic is expressed by a curve. As a result, a battery characteristic curve of the battery set can be established for comparison. The characteristics of the each battery of the battery set can be thus judged by the interval between the curves.
The advanced method described above is defective in design in that the curves are numerous, and that the size scale must be enlarged appropriately to avoid an erroneous reading, and further that the curves do not reveal the residual capacity of any one of the batteries of the battery set, and further that it is a time-consuming task requiring 50 to 60 minutes to finish the charging and the discharging tests.